Most people need not worry about RollJam. "With cars, most criminal elements are just going to break your window, unlock the door, and steal your stuff," said Adam Wosotowsky, a messaging data architect with Intel Security. "If you're willing to steal from someone's car, then you're probably not the kind of criminal that does a lot of preplanning for your target."

A gadget that can intercept wireless signals to unlock cars and garage doors was displayed at the recent DefCon conference in Las Vegas. Security researcher Sammy Kamkar showed off the device, dubbed ‘RollJam’which cost him just US$32 to make.

The wallet-sized gadget works by intercepting the wireless signal and storing the unlock code sent from a key fob to open a vehicle or garage door.

To the person trying to open the door, it appears that the fob has failed. Typically, that will prompt the person to press the fob again. RollJam blocks that transmission, too, but at the same time sends the first intercepted code to the door.

To the person opening the door, it appears as if the second fob press opened the door. The individual remains unknowing that a hacker has captured the code and can later use it to open the vehicle or garage.

RollJam works with a wide array of motor vehicles and garage door openers, according to Kamkar. In fact, the device can compromise any hardware that uses the KeeLoq access control system from Microchip Technology, the High Security Rolling Code generator made by National Semiconductor, and Hisec chips sold by Texas Instruments.